Voltage regulators, such as DC-to-DC voltage converters, are used to provide stable voltage sources for various electronic systems. Efficient DC-to-DC converters are particularly needed for battery management in low power devices (e.g., laptop notebooks, cellular phones, etc.). A switching voltage regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and then filtering the high frequency input voltage to generate the output DC voltage. Specifically, the switching regulator includes a switch for alternately coupling and decoupling an input DC voltage source (e.g., a battery) to a load (e.g., an integrated circuit (IC)). An output filter, typically including an inductor and a capacitor, may be coupled between the input voltage source and the load to filter the output of the switch, and thus provide the output DC voltage. A controller (e.g., a pulse width modulator, a pulse frequency modulator, etc.) can control the switch to maintain a substantially constant output DC voltage.
A switch mode power supply can theoretically approach 100% power conversion efficiency when the switching devices and filtering devices have zero loss. The switch mode power supply is thus becoming more popular than the linear regulator because of its relatively high efficiency. Conventional switch mode power supply topology may have at least one inductor for each regulated output. A drawback of this approach is that a number of inductors, as well as an overall solution size of the power management devices, can be too large to be accommodated into today's compact electronics devices. In addition, the costs of such solutions can be too high to be practically viable in cost sensitive consumer applications.
For linear device based regulators, most outputs may be regulated by linear power devices, thus allowing for elimination of the inductors. However, the resulting power losses in the power conversion can be so substantial that battery run time may be severely limited. In addition, the relatively large voltage differential between the input voltage and the output supply rail may cause the linear regulator devices to heat up substantially, thus presenting a thermal management challenge. If an additional heat sink is needed, the resulting overall solution size can be too large to fit into a compact electronic device (e.g., a cell phone).